1. Field of the Invention
The present invention relates to improvements in a heating device for fuel injected from a fuel injection valve of an electronic control type in an internal combustion engine.
2. Description of the Prior Art
It is well known that electronic fuel injection systems are now used in internal combustion engines for automotive vehicles in order to improve the responsive and emissive performance of the engine by precisely adjusting air-fuel ratio. Furthermore, some of such engines are provided with heating devices for heating fuel injected from fuel injection valves in order to promote vaporization of fuel. Such a heating device is disclosed, for example, in Japanese Patent Provisional Publication No. 56-6056. The heating device is provided with a cylindrical body and a PTC (Positive Temperature Coefficient) heater. The cylindrical body is made of aluminum alloy and fixed to an inner surface of an intake port of an internal combustion engine. The PTC heater is embedded in the cylindrical body and connected to a battery which provides current. The cylindrical body is disposed downstream of a fuel injection valve such that fuel injected from the fuel injection valve passes through the cylindrical body. Accordingly, at a start time of the engine, the injected fuel is heated by the heating device in order to accelerate the vaporization of the injected fuel.
However, with the above-mentioned heating device, since only an inner surface of the cylindrical body contributes to the heating of the injected fuel, it is not sufficient to heat the injected fuel effectively. That is, the cylindrical body can not sufficiently heat up the injected fuel passing through the central part of therein.